1. Field of the Invention
The present invention relates generally to disinfectant systems for swimming pools, spa water, cooling tower water and other aqueous media. More particularly, the invention relates to systems utilizing chlorine as a disinfectant, and to compositions and methods for inhibiting the production of chloramines and trihalomethanes in such systems.
2. Background
It is known to the art that swimming pools, spa water, cooling tower water and other aqueous media require chemical sanitation. Chlorine, in various forms, is the most widely used chemical for this purpose, being both economical and highly effective for bacteria and algae control. The use of chlorine presents certain problems however, including the need to stabilize the chlorine to prevent its depletion over an extended period of time.
In addition, it is known that eye and skin irritation may be caused by swimming pools and/or spas using chlorine-based sanitation systems. Also, undesirable odors may result when such sanitation systems are employed. The most common of these problems is caused by the formation of irritating and odorous dichloramines and possibly trichloramines. These compounds may be formed in reactions with organic or inorganic nitrogen-containing compounds such as urea, creatinine, uric acid, amino acids, etc., which may be introduced into the water by bacteria, algae, insects, air or swimmers.
Not only do chloramines have disagreeable odor and irritational properties, they are much less effective as biocides than hypochlorous acid. In particular, chloramines are reported to be only 1/80th as biocidally active as free available chlorine.
It is known to the art that chloramine formation is promoted when the pH of the water is at least slightly acidic. Because it is not uncommon for swimming pool waters to become acidic, chloramines form easily therein. In addition, the presence of nitrogen-containing compounds in swimming pool water promotes chloramine formation since favorable nitrogen-to-chlorine ratios commonly exist in such waters.
The production of chloramines in aqueous media has been inhibited in prior art systems by superchlorination--the application of a "shock" dose of free available chlorine (e.g., 10 ppm) to pool water to oxidize organic and inorganic nitrogenous and other wastes from the water. This method does not extend the useful life of the chlorine, and may cause eye and skin irritation problems of its own.
It is also known that trihalomethanes, such as chloroform, may be present in swimming pool waters treated with conventional chlorine-source compositions. These compounds not only cause eye and skin irritations, at certain concentrations they are toxic by inhalation. Even at concentrations insufficient to be toxic, trihalomethanes have distinctive odors which are objectionable for certain applications.
A need therefore exists for a method of inhibiting the formation of chloramines, trihalomethanes and odors in aqueous systems while stabilizing the chlorine in the water. The present invention addresses that need.